Syrian opposition urges US to act on 'red line' in chemical weapons issue

En esta foto del 22 de septiembre de 1973 se ve el minarete de la mezquita Umayad en Alepo, Siria. La prensa estatal siria y activistas opositores dijeron que el minarete fue destruido, aunque las dos partes lo atribuyen a sus adversarios (AP Foto/Azad, Archivo) (The Associated Press)

This March 6, 2013 citizen journalism image provided by Aleppo Media Center AMC which has been authenticated based on its contents and other AP reporting, shows the minaret of a famed 12th century Umayyad mosque before it was destroyed by the shelling, in the northern city of Aleppo, Syria. The minaret of a famed 12th century Sunni mosque in the northern Syrian city of Aleppo was destroyed Wednesday, April 24, 2013. President Bashar Assad's regime and anti-government activists traded blame for the attack against the Umayyad mosque, which occurred in the heart Aleppo's walled Old City, a UNESCO World Heritage site.(AP Photo/Aleppo Media Center, AMC) (The Associated Press)

Esta imagen tomada de video obtenido del Aleppo Media Center AMC, el cual ha sido autentificado con base en su contenido y otros reportes de la AP, muestra la famosa mezquita Umayyad del siglo XII, la cual fue dañada por bombardeo, en el norte de la ciudad de Alepo, Siria, el miércoles 24 de abril de 2013. (Foto AP/Aleppo Media Center, AMC) (The Associated Press)

Syrian opposition figures are urging the U.S. to act on President Barack Obama's own public assertions that Syria's use of chemical weapons would cross a "red line."

The White House and other top Obama administration officials said Thursday that U.S. intelligence has concluded with "varying degrees of confidence" that the Syrian government has twice used chemical weapons in its civil war.

Ahmad Ramadan, a member of the Syrian National Coalition opposition group's executive body, called the U.S. assertion an "important step" that should be followed by actual measures taken by the U.N. Security Council and Friends of Syria group.

Ramadan told The Associated Press by phone from Istanbul that the U.S. has a "moral duty" to act to prevent President Bashar Assad from using more chemical weapons.